LMP gene promoter hypermethylation is a mechanism for its down regulation in Kazak's esophageal squamous cell carcinomas.

Abnormal hypermethylation of CpG islands not only associated with tumor suppressor genes can lead to repression of gene expression, but also contribute to escape of the tumor from immune surveillance and contribute significantly to tumorigenesis. In the present study, we studied the hypermethylation of low molecular-weight protein (LMP) gene and its regulation on protein expression in biopsies from resected tissues from Kazak's esophageal squamous cell carcinoma (ESCC) patients and their neighboring normal tissues. LMP2 and LMP7 genes promoter region methylation sequences were maped in esophageal cancer cell line Eca109 by bisulfite-sequencing PCR and quantitative detection of methylated DNA from 30 pairs of Kazak's ESCC and adjacent normal tissues by MassARRAY (Sequenom, San Diego, CA, USA) and LMP2 and LMP7 protein expression were analyzed with immunohistochemistry. In Eca109, we identified 6 CG sites methylated from all of 22 CpG sites of LMP7 gene. However, no methylation was found for LMP2. The analysis of the data resulted from the quantitative analysis of single CpG site methylation by Sequenom MassARRAY platform, has shown that the methylation level between two groups CpG sites (CpG_5, CpG_9, CpG_20, CpG_21 and CpG_20) from CpG_1, CpG_2, CpG_3, CpG_4, CpG_5, CpG_6, CpG_7, CpG_8, CpG_9, CpG_10.11, CpG_12.13.14, CpG_15.16.17.18, CpG_19, CpG_20, CpG_21 and CpG_22 significant differences between ESCC and neighboring normal tissues. The analysis of methylation level of whole target CpG fragment indicated that the methylation level of LMP7 was significant higher in ESCC (0.0517 ± 0.0357) than in neighboring normal tissues (0.0380 ± 0.0214, P < 0.05). there was a tendency of decreasing the LMP7 proteins expression as the increasing the methylation level of LMP7 gene promoter regions (F = 7.69, P = 0.041). The LMP7 gene promoter methylation and protein downregulation were correlated at high extent in Kazakh's ESCC patients, and may explain the epigenetic regulation on gene expression.